Lithium-ion secondary batteries have energy density higher than conventional secondary batteries, and can function with high voltage. Thus, lithium-ion batteries are used for information devices such as cellular phones as secondary batteries easy to be made to be small and light. Also, increasing these days is the demand for lithium-ion batteries as power for large-sized machines such as electric vehicles and hybrid vehicles.
A lithium-ion secondary battery has a positive electrode layer, a negative electrode layer and an electrolyte layer arranged between them. As an electrolyte used for an electrolyte layer, for example, liquid or solid non-aqueous substances and the like are known. When a liquid electrolyte (hereinafter referred to as “electrolyte solution”) is used, the electrolyte solution is easy to permeate the positive electrode layer and the negative electrode layer. Thus, interfaces between the electrolyte solution and active materials contained in the positive electrode layer and negative electrode layer are easy to form, and the performance of the lithium-ion secondary battery is easy to be improved. However, since widely used electrolyte solutions are combustible, it is necessary to equip a lithium-ion secondary battery with a system to secure safety. On the other hand, when a solid electrolyte that is incombustible (hereinafter referred to as “solid electrolyte”) is used, the above described system can be simplified. Therefore, progress is being made in the development of a lithium-ion secondary battery that has a layer containing a solid electrolyte (hereinafter referred to as “solid electrolyte layer”) (such a lithium-ion secondary battery may be referred to as “all-solid-state battery” hereinafter).
As an art concerning solid electrolytes that can be used in all-solid-state batteries as described above, for example, Patent Literature 1 discloses the art of manufacturing Li2S—P2S5 based crystallized glass (lithium ion conductive sulfide based crystallized glass) by means of a mechanical milling method.